New pilots who buy their copilot time are buying a service. They can only fly with qualified training captains and are very much a liability until they are checked out, which takes a long time. They are then inexperienced, and without being rude, a liability to line captains because of their lack of knowledge, breadth and depth. It takes time to be an adequately contributing member of crew, particularly in a 2 member crew. You're buying that support and training.
As for people paying for their own rating, what is the problem with understanding it is a free country? People have the right, and if it makes them more employable, well, they have got something back for their investment in themselves, haven't they? It should be banned because you can't go that far? If you want to ban this, why not ban altogether paying for your own flying training? Airlines would recruit the most talented ab initios, not the ones who just put together 80k whether they have aptitude or not? The airlines would have to pay for training, but you would not decide whether you were to proceed in a career. So why is it OK for you lot to stop others paying one stage more when you've ALL paid for training anyway?
Stop being jealous and hysterical. You have no argument. Accept that you cannot afford the extra with grace and find a way around it. You may have to wait longer. But the kid with no assets can equally point a finger at you and say 'why should you be able to buy your training and put yourself at an advantage to me who can't afford any of it?'